From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.remote-ip=100.103.45.18 ARC-Seal: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; cv=none; t=1792776479; b=zzmxwcaC/PkK0OEgPnnaqZUpxU72yDwW/Czw3JeaXDnOn7UTl4Cl1xjP1kMdPN8qJoZx KmZtSFVdXikTWD46xI6isA7q6tAutOgdqBj92a95o+6F43WVviryIqdJM/cVodrqbZJJf jWM+cIQiC9q2uGYrph4BT74keXdIF2Xsb1SHQhnEbJmICm9t9nYGWbRpnchf5aXrZndUv 0SRx0dmuhq/qGLIGe4e61anQQqPltUqZwBWI0etPd13PONtkc53dJOvpgscBh8Zy9bdy5 QmenvPDmmqAN1f4faeXVRQAWenzBPM4YGPVKOG35yff3dPTZgdFMYNpgFSLI/8yQYXQ== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1792776479; h=Received:DKIM-Signature:Date:From:To:Cc:Subject:Message-ID: In-Reply-To:References:MIME-Version:Content-Type: Content-Transfer-Encoding; bh=jJXUDdGOUlnprTLNQ3mpD2znb8kn6x0W43UYG81DLJE=; b=u51EQVR1R+dEPPggXOJoET1mZWVzkp731M/2d9tbLggsea+3yPklRnK8QQPS6tK0nkjK 5tAYR+wKvASCVPTyz8Cp365QWCVe0OprRbxv6r4KbJH+JrrOqJnhnmxrOuaxy0FytRshf cNdZa9UtXPxFS+5vU2IB078evadl2gmUHTVsI/Ab2SBX8Zkw0FtM+P7OXzdSprUF2Nyni 5TodNc2Xh8qsbrifsEyFZkP4PI5KkKUwsc9Lz+qnUwhLV0mlCy5m+zKz7Cj11vW7SQTd4 s0dVHBAUXzHgIpbLiIsdS7Yi5MUEoXGiRGaqWJjfZGgvxy4OHDJCO/B1WB2/L/+QfJA== ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=VRNOxv+1; arc=none smtp.remote-ip=100.103.45.18 Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (prime256v1)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id A3920606A31A; Fri, 23 Oct 2026 17:27:58 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key, unprotected) header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=VRNOxv+1 Received: by smtp.kernel.org (Postfix) with ESMTPSA id 68DAF1F01825; Fri, 23 Oct 2026 17:27:57 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1792776478; bh=jJXUDdGOUlnprTLNQ3mpD2znb8kn6x0W43UYG81DLJE=; h=Date:From:To:Cc:Subject:In-Reply-To:References; b=VRNOxv+1Pksyrz5HnFhBkcnpuxCnSmnXdeyB52HziAZ0BKiZZtXPxAuj93PuJc5xI 1pTqs+75q+CJrl3PdpXqmb75U0b0ztZJPlKfMeA3oNQiv6FTGN0ztfopW9p+8p+T7P ui7Qx8f3vVvVIwafvbWaB9RjhsPkzk6toCmg6ljNO/fs5AQqJlScIW/CdQo43D6NRP tJo7uzYkrsViniHWvZsVkJCO1YIV9hAIclTxvK4nIj4FUgUlALsK4u9HNWRALjqoHb Ctem5QTw0r4Gw3aGxKfIafMxkmpl9sspL0EJ5FfAFmnB/0QSTga0iibcftCdkkp4By uoxDdS6wkAlbA== Date: Fri, 23 Oct 2026 10:27:56 -0700 From: Jakub Kicinski To: Jason Gunthorpe Cc: Luigi Rizzo , "David Hildenbrand (Arm)" , Luigi Rizzo , Joerg Roedel , Will Deacon , Robin Murphy , Christoph Hellwig , Marek Szyprowski , Andrew Morton , Vlastimil Babka , "David S . Miller" , Eric Dumazet , Paolo Abeni , Greg Kroah-Hartman , "Rafael J . Wysocki" , Danilo Krummrich , Jonathan Corbet , Jesper Dangaard Brouer , Ilias Apalodimas , Willem de Bruijn , Kuniyuki Iwashima , Joshua Washington , Harshitha Ramamurthy , Saeed Mahameed , Tariq Toukan , Tony Nguyen , Przemek Kitszel , Alexander Lobakin , Michael Chan , Pavan Chebbi , iommu@lists.linux.dev, netdev@vger.kernel.org, linux-mm@kvack.org, driver-core@lists.linux.dev, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [RFC: DMA_PMD 00/22] DMA_PMD: PMD_SIZE-backed IO buffer pools Message-ID: <20261023102756.201315d7@kernel.org> In-Reply-To: <20261023145023.GH3977851@ziepe.ca> References: <20261003212241.3432303-1-lrizzo@google.com> <0cc1cac1-a500-489b-9c1b-b49598b5550b@kernel.org> <20261022201229.GH3381610@ziepe.ca> <20261023140107.GC3977851@ziepe.ca> <20261023145023.GH3977851@ziepe.ca> X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit On Fri, 23 Oct 2026 11:50:23 -0300 Jason Gunthorpe wrote: > > Anyways, reading your next comments, are you suggesting that all > > these functionalities should be implemented as pagepool extensions? > > (2MB mappings and iommu backing, proper allocator of fragments out of larger > > pages, device-less pagepools, multi-domain mappings, pagepool > > as memory provider for skb heads, pagepool as memory provider for descriptor > > rings ?) > > netdev shouldn't be touching iommu, it can get a 2M page and map it > using the normal DMA API. AFAIK there is not such a big reason to need > any of these layering violations. They just make it easier on page > pool.. FWIW we're entirely happy on the netdev side to add this to page pool. In fact the initial RFC I posted for "page pool memory providers" was addressing this exact use case. I didn't push it forward due to low time and suspicion that IOMMU folks would prefer a more generic solution. Since then memory providers were pushed forward and merged for dmabuf, and we have netlink APIs to configure things. So adding large mappings should be SMOC.